I made some long a-frame type outfits out of PVC with foam padding that slide under ours to keep the water from pooling, BUT, we full time, and they are under there for long periods of time. I wouldn't bother if we were weekend warriors. Ideally, you'd just install the toppers with more pitch if doing yourself. Just did my father in laws and made enough pitch to avoid the pooling. Not enough pitch on mine since the rail went over where the old gutter above the slide was.
John and Rebecca Dickson
Emma-8 / Little John-5 / Iva-1+
2013 Ford F-350 Lariat FX4, CC LB PSD, DRW
2015 Jayco Jay Flight 28BHBE (#8)